Abstract:Trophic groups of soil nematodes were investigated in the rhizosphere and non-rhizosphere of Vetiveria spp. and Pennisetum spp. in South China Botanical Garden. Soil nematodes were aggregated mainly in the soil layer of 0-15 cm regardless of the biomass and the length of roots of Vetiveria and Pennisetum，and the densities of bacterivores and phytophages were significantly higher than those of the other three trophic groups, fungivores, omnivores and predators in all habitats. The proportions of bacterivores and phytophages were in the range of 87.7-97.6% and 88.5%-94.0% and those of the other three trophic groups were 2.4%-12.3% and 6.0%-11.5% under grasses of Vetiveria spp. and Pennisetum spp., respectively. The total number of nematodes was much higher in the rhizosphere than in the non-rhizosphere of grasses of Vetiveria, but this was not so obvious under grasses of Pennisetum. The proportions of phytophages under Vetiveria and under hybrid Pennisetum (P. americanum × P. purpureum) were much higher in the non-rhizosphere than in the rhizosphere, while the proportions of bacterivores were much higher in the rhizosphere than in the non-rhizosphere. Nevertheless, the proportions of phytophages and bacterivores under king grass (P. purpureum × P. thyphoides) and elephant grass (P. purpureum) habitats were opposite to that under Vetiveria. The proportions of fungivores were higher in the non-rhizosphere than in the rhizosphere under both genera of Vetiveria and Pennisetum with the exception of king grass. Higher nematode densities were found under V. zizanoides var. Karnataka and hybrid Pennisetum, indicating that the two species have good potential for the improvement of soil fertility.
